Plastic fuel tanks typically include a hollow body having one or more openings, and a plurality of fuel system components disposed in the interior of the body such as individual pumps, valves, and the like. The components may be inserted through the one or more openings, or may be molded in the interior of the body when the tank is manufactured. In some applications, one or more of the components may be mounted on a carrier that is inserted between molds in an interior of a parison that is blow molded around the carrier and into conformity with the molds. The carrier typically has standoffs or feet that contact corresponding portions of the tank to position and support the carrier within the tank. But such a carrier is basically another component to be supported within and by the walls of the fuel tank.
In use, fuel vapors in the tank are typically vented for temporary storage in a carbon canister until the vapors can be purged into the engine. But in some vehicle applications it is desirable to limit such venting of vapors and, as a result, the fuel tank may become pressurized which may be damaging to a tank.